Balanced slide-valve



(No Model.) Y 3 Sheets-Sheet l. P. MGDERMOTT.

BALANGBD'SLIDE VALVE.

Patented Sept. 2, 1884,

, m. al.

l 1 E I IIIIIIIIIIIIIIIIH .IWMITO (No Model.)

' 3 Sheets-Sheet 2. P. MODERMOTT.

BALANGED SLIDE VALVE.

Patented Sept. 2,1884.

IIIUDKIIUIUIIIIIIIIUlllllllIlll Hilllllllllllllllllllllllllfl5 (NoModel.) 3 Sheets-Sheet 3.

P. MGDERMOTT. BALANGBD SLIDE VALVE.

E all lll PATRICK MCDERMOTT, OF MEMPHIS, TENNESSEE.

BALANCED SLIDE-VALVE.

EJPECIFICATION forming pari; of Letters Patent No. 304,338, datedSeptember 2, 1884.

Application filed March 7, 1884.

(No model.)

slide-valves attempted to be used'before my invention is that in whichcircular packingrings are attached to the back of the valve to form aso-called steam-tight joint77 with the steam-chest cover, or with aplate fastened to the steam-chest cover. This form is objectonable inactual use by reason of the necessity which exists of frequentadjustment, the

impossibility of proper adjustment with steam in the steam-chest, andthe great difficulty in maintaining the joints steam-tight for anyreasonable length of time. It has also been attempted to balance orrelieve the pressure on slide-valves by the employment of a relief orpressure plate, between which and the valvel seat the valve works, therelief-plate being fixed rigidly to projections cast in the steamchest.This method of balancing has been found very objectionable on accountofthe necessity of having to set the relief-plate very frequently, andthe extremely difficult task of making a sufficiently tight joint, whileat the same time allowing the valve sufficient room to work in withoutbinding. With this form, also, the fact that the valve cannot leave itsseat when working with water in the cylinder causes disastrous results.In my improvement a relief or pressure plateis employed, between whichand the valve-seat the slide-valve works, this relief-plate beingsupported by suitable connecting devices from a second or balancingcylinder, the pressure in which'varies .directly with that in thesteam-chest or supply-pipe, thus rendering the pressure of the plateupon the valve always constant. The relief-plate is supported from alever having a movable fulcrum to enable adjustment, according to therelative pressure-areas of the relief-plate and the balancing-cylinder,the resultant being always allowed to be slightly in favor of downwardpressure on the relief-plate, in order to secure a steam-tight joint,while allowing such freedom of movement as to prevent great friction andconsequent wear. Novel means are provided for connecting tliereliefplate and the piston of the balancing-cylinder and for maintainingthe relief-plate against the slide-valve independently of the force ofthe steam. production of asystem, among the advantages of which aresimplicity, durability, economy, effectiveness, and easy adaptability toengines of various constructions.

In order that my invention may be more fully understood, I-will proceedto describeit with reference to the accompanying drawings, whichrepresent the invention applied to an engine in which is employed a Dslide-valve of ordinary double form. Corresponding to this form of valveemployed, all'the parts of the balancing device are made in duplicate.Should a single valve be employed, such duplication would, in general,be unnecessary.

In the following description, when describing any of the parts of thebalancing device, it will be understood without further explanation thatthe part will be duplicated or not, according to the necessities of thecase.

Figure I is a transverse sectional view of a stationary engine with myimprovement applied, the section being taken on the line I I, Figs. IIand III. Fig. II is a side elevation of the same. Fig. III is ahorizontal sectional view on the li ne III, Figs. I and II. Fig. IV is aperspective view of the relief-plate, and Fig. V is a similar viewshowing the form of slide-valve here employed. Fig. VI is a detail of amodification of the relief-plate guides.

1 is the cylinder, 2 the bed or base, 3 the steam-chest, and et thesteam-chest cover, of an engine, all of which parts may be oftherepresented or any preferred construction.

The slide-valve 5 (see Fig. V) is of the ordinary D form, with a flatback, whiehmay be, as here shown, formed in one piece with the valve; orthe same result can be obtained by bolting with countersunk bolts a flatyplate to the back of any oval-backed valve. The back of the valveshould be of the same area as the seat-face of the valve, and both facesshould be planed true and parallel.

The relief or pressure plate 61's so constructed, when used for thedouble valve, as to have two surfaces or plates equal in areato and thesame distance apart as the valve-seat faces. The two parts of the plateare connected by bars 7, formed integrally therewith or rigidly Xedthereto, and extending along the back of the plate and longitudinally ofthe Valve. Said The result of theimprovements is the ICC bars 7 (or asmany thereof as may be necesl allowed said plate-causing a correspondingsary) extend beyond the ends of the plate, as seen in Fig. IV, to theends of the steam-chest, and are there dressed off, so as to nicely fitwithout binding, thus holding the plate from longitudinal whilepermitting its vertical movement. If desired, the extended bars 7 may bemade shorter than the steam-chest, in

which case their ends would be tapped, as shown in Fig. VI, forregulating-screws S. By turning outthe screws 8 lost motion of the platelongitudinally can be taken up and the position of the plate readilyadjusted. The bottom, or that face of the plate which lies next thevalve,shouldbeplanedtrueand straight. Inthe center of the back of therelief-plate 6 are cast bosses 9, for the reception of stems or rods 10,which are fastened toy said bosses by screw, ball and socket, orotherwise. The rods 10 pass through stuffing-boxes 11, attached tosteam-chest cover 4 by steam-tight screws, bolted flanges, or otherwise,andthe other end of' said rod is connected by ball-and-socket or otherpivotal joint, 12, to one end of a lever, 13, fulcrumed on block 14, andconnected by similar joint, 15, to a piston-rod, 16. 'Ihe piston-rod 16passes through stuffing-box 17 in the balancing-cylinder 18, where it isfixed to piston-head 19, which is packed within said cylinder.

Communication with the steam-chest for the admission of steam to actagainst piston-head 19 is had by a neck, 20, fixed to the cylinder 18and to the steam-chest by screwing, bolting, or other manner to produceasteam-tight joint. Any waste steam or water that may escape past thepiston-head 19 is allowed to run off by pipe 21.

Attached to and forming part of the steam-l chest cover 4, either bybeing cast in one therewith or by bolting, are seats 22, having a slot,23, undercut to receive the head 24 of a bolt, 25, by means of which thefulcrumblock 14 may be clamped firmly to place and adjusted in position'vertically, as required, a tongue, 26, on the bottom of' the blockoccupying the slot 23, to permit vertical while denying lateralmovement. It will be seen that a wide range of adjustment transverselyacross the steam-chest cover is allowed the fulcrum-block 14. Byshifting the fulcrum the balance-cylinder may be made to more or lesscompletely balance the pressure in the relief-plate, the force ofbearing of the same on the valve being thus under the control of theengineer. In Fig. III one of these fulcrums 14 is removed from its seatand shown in side and end elevation.

Att-ached to the inside face of the steamchest cover by bolt orotherwise is an elliptic steel spring, 27, to hold the plate and valveto proper position.

From the foregoing it will now be apparent that the pressure of thesteam in the steam-chest would, if unrestrained, exert a great force inpressing the relief-plate against the valve-freedom of vertical motionbeing friction on the valve, and consequent wear and loss of force. Thispressure is, however, counterbalanced to a greater or less extent atwill by the cylinder 18 and the connecting mechanism above described,the conditions remaining the same, no matter what may be the varyingpressure of the steam. This system, after being once regulated to theneeds of a particular engine, needs no more attention in that respect,the mechanism being selfadjusting to all changes of pressure.

I do not limit myself to the precise construction shown or described;but I desire it to be understood that I claim any construction whichshall embody and contain the spirit and substance of my invention.

Having thus described my invention, the following is what I claim as newtherein and desire to secure by Letters Patent:

l. The combination of a valve-chest containing a sliding D-valveand arelief-plate overthe same, a balancing-cylinder communicating at one endonly with lthe valve-chest, a piston working in said balancing-cylinder,and mechanism for connecting the said piston with the relief-plate,substantiall y as and for the purpose set forth.

2. In combination with the slide-valve and a relief-plate over the samehaving liberty4 of vertical movement, a balancing-cylinder connectedwith the steam chest by a suitable duct, a piston working in saidbalancing-cylinder, a rocking lever connecting the stem of said pistonwith the stem of' the relief-plate,

and a fulcrum on which said rocking lever rests, substantially las andfor the purposes set forth.

3. In combination with the slide-valvel and a relief -plate over thesame having liberty of' vertical movement, a balancing-cylinderconnected to the steam-chest by a suitable duct, a piston working insaid balancing-cylinder, a rocking lever connecting the stem of saidpiston with the stem of the relief-plate, and an adjustable fulcrum onwhich said rocking lever rests, whereby the pressure of the relief-plateon the valve is automatically balanced or relieved, as explained. u

4. The combination of' a relief-plate, a balancing-cylinder, a lever,and suitable connections with an adjustable fulcrum-block, for thepurpose set forth.

5. In combination with slide-valve-balancing mechanism, substantially asdescribed, a slotted fulcrum-seat on the steam-chest, a removablefulcrum having a fin entering Said Slotted way, and a clamping bolt andnut,

substantially as and for the purpose set forth. 6. Inslide-valve-balancing mechanism, the relief-plate fitted at its endswith adjustingscrews for taking up wear, as and for the purpose setforth.

PATRICK MCDERMOTT.

Vitnesses: l

FRANK BLOMBERG, II. G. Fox.

ICO

IIO

